Crustin expression following bacterial injection and temperature change in the shore crab, Carcinus maenas.

The expression of carcinin, a crustin-type antimicrobial protein, in the crab, Carcinus maenas, was studied following in vivo challenge with Planococcus citreus, a Gram-positive bacterium known to be killed by the encoded protein. Real-time PCR analyses reveal that injection of P. citreus failed to elicit any significant changes in expression at 0-24h post-injection although there was a small, but significant, down-regulation at 84h in crabs held at 15 degrees C but not those at 5 or 20 degrees C. By contrast, un-injected crabs held at various temperatures between 5 and 20 degrees C, showed significantly up-regulated expression at 5 and at 20 but not 10 degrees C compared with controls at 15 degrees C. Thus expression of carcinin seems to be affected by temperature, especially when the animal is close to the edges of its physiologically tolerated thermal range.

Localization and diversity of 185/333 proteins from the purple sea urchin--unexpected protein-size range and protein expression in a new coelomocyte type.

The current paradigm proposes that the innate immune systems of invertebrates are much more complex than previously thought. The highly diverse 185/333 gene family in the purple sea urchin encodes a family of closely related proteins of varying length and sequence composition. Subsets of small phagocytes and polygonal cells express 185/333 proteins with localization on the surface of the small phagocytes and within perinuclear vesicles in both cell types. In short-term cultures, coelomocytes form small aggregates that progress to syncytia that are thought to be equivalent to encapsulation in vivo. These aggregates were found to be enriched for 185/333-positive (185/333(+)) small phagocytes. In response to lipopolysaccharide challenge, coelomocytes transiently increased, including frequencies of both 185/333(+) and 185/333-negative (185/333(-)) small phagocytes and 185/333(+) polygonal cells. The 185/333 proteins were present in a broad array of sizes, most of which were larger than that predicted from the cDNAs. Recombinant 185/333 proteins expressed in bacteria and insect cells were also larger than expected, suggesting that the proteins dimerize and multimerize. The diversity of the 185/333 proteins, their expression in response to immune challenge, and their cellular localization suggests this protein family and the small phagocytes have an important immunological role in the sea urchin.

Distinctive expression patterns of 185/333 genes in the purple sea urchin, Strongylocentrotus purpuratus: an unexpectedly diverse family of transcripts in response to LPS, beta-1,3-glucan, and dsRNA.

BACKGROUND: A diverse set of transcripts called 185/333 is strongly expressed in sea urchins responding to immune challenge. Optimal alignments of full-length 185/333 cDNAs requires the insertion of large gaps that define 25 blocks of sequence called elements. The presence or absence of individual elements also defines a specific element pattern for each message. Individual sea urchins were challenged with pathogen associated molecular patterns (PAMPs) (lipopolysaccharide, beta-1,3-glucan, or double stranded RNA), and changes in the 185/333 message repertoire were followed over time. RESULTS: Each animal expressed a diverse set of 185/333 messages prior to challenge and a 0.96 kb message was the predominant size after challenge. Sequence analysis of the cloned messages indicated that the major element pattern expressed in immunoquiescent sea urchins was either C1 or E2.1. In contrast, most animals responding to lipopolysaccharide, beta-1,3-glucan or injury, predominantly expressed messages of the E2 pattern. In addition to the major patterns, extensive element pattern diversity was observed among the different animals before and after challenge. Nucleotide sequence diversity of the transcripts increased in response to beta-1,3-glucan, double stranded RNA and injury, whereas diversity decreased in response to LPS. CONCLUSION: These results illustrate that sea urchins appear to be able to differentiate among different PAMPs by inducing the transcription of different sets of 185/333 genes. Furthermore, animals may share a suite of 185/333 genes that are expressed in response to common pathogens, while also maintaining a large number of unique genes within the population.

Gene characterisation, isoforms and recombinant expression of carcinin, an antibacterial protein from the shore crab, Carcinus maenas.

Carcinin is a whey acidic protein (WAP) domain-containing antimicrobial protein produced by the circulating haemocytes of the shore crab, Carcinus maenas. Cloning of its full coding cDNA reveals that it shows some similarity to invertebrate defensins, has a valine-rich signal sequence followed by a defined cleavage site but no obvious acidic anionic 'pro' sequence. The C-terminus exhibits a unique cysteine array that is predicted to form six disulphide bonds in the tertiary structure. This 12 cysteine array arrangement is conserved in expressed sequence tags (ESTs) from related genera and seems to represent a novel tertiary structure amongst antimicrobial proteins (AMPs), unique to the Crustacea. There are at least five putative isoforms that arise through the transcription of a multi-exon gene. These isoforms do not arise as a result of alternate splicing of the exons, but by either the transcription of different alleles and/or single point mutation of the transcript at up to four loci in the gene. Several of the same transcripts have been found in different animals. The most commonly expressed transcript of the protein was recombinantly expressed in bacterial fusion system to a yield of ca. 2-3 microg ml(-1) of culture. In vitro expression with or without the leader sequence confirms the bioinformatic prediction that the stability of the mature protein is reduced when the leader sequence is removed. Carcinin is one of very few invertebrate AMPs characterised at the gene, transcript and protein level and to be recombinantly expressed in vitro in a bacterial system.

The immune gene repertoire encoded in the purple sea urchin genome.

Echinoderms occupy a critical and largely unexplored phylogenetic vantage point from which to infer both the early evolution of bilaterian immunity and the underpinnings of the vertebrate adaptive immune system. Here we present an initial survey of the purple sea urchin genome for genes associated with immunity. An elaborate repertoire of potential immune receptors, regulators and effectors is present, including unprecedented expansions of innate pathogen recognition genes. These include a diverse array of 222 Toll-like receptor (TLR) genes and a coordinate expansion of directly associated signaling adaptors. Notably, a subset of sea urchin TLR genes encodes receptors with structural characteristics previously identified only in protostomes. A similarly expanded set of 203 NOD/NALP-like cytoplasmic recognition proteins is present. These genes have previously been identified only in vertebrates where they are represented in much lower numbers. Genes that mediate the alternative and lectin complement pathways are described, while gene homologues of the terminal pathway are not present. We have also identified several homologues of genes that function in jawed vertebrate adaptive immunity. The most striking of these is a gene cluster with similarity to the jawed vertebrate Recombination Activating Genes 1 and 2 (RAG1/2). Sea urchins are long-lived, complex organisms and these findings reveal an innate immune system of unprecedented complexity. Whether the presumably intense selective processes that molded these gene families also gave rise to novel immune mechanisms akin to adaptive systems remains to be seen. The genome sequence provides immediate opportunities to apply the advantages of the sea urchin model toward problems in developmental and evolutionary immunobiology.